Using nicotine replacement therapy to assist in reducing cigarette consumption before quitting: another strategy for smoking cessation?

McRobbie H, Whittaker R, Bullen C

CRD summary

This review, which assessed the efficacy of nicotine replacement therapy (NRT) in reducing cigarette consumption in smokers before quitting, concluded that NRT is effective and can lead to long-term cessation, which should remain the ultimate goal. Given several limitations of the review (such as potential reviewer bias), and the limited study details and data synthesis, the authors' conclusions may not be reliable.

Authors' objectives

To assess the efficacy of nicotine replacement therapy (NRT) in reducing cigarette consumption in smokers before quitting.

Searching

MEDLINE and PsycINFO were searched from January 1990 to August 2006; the search terms were not reported.

Study selection

Randomised controlled trials (RCTs) comparing the use of NRT with placebo to aid smoking reduction, and reporting cessation data as the outcome, were eligible for inclusion. Studies assessing the use of NRT as a cessation method prior to quitting were excluded. The included studies were of smokers aged at least 18 years who had consumed 15 or more cigarettes per day for 3 years or more, and who wanted to reduce their consumption but were unwilling to quit within the next month. With the exception of one study, the included studies assessed abstinence rates using 7-day point prevalence abstinence. The duration of the intervention ranged from 6 to 18 months and follow-up ranged from 6 months to 2 years. NRT was administered as a patch or gum or by inhaler.

The authors did not report how the papers were selected for the review, or how many reviewers performed the selection.

Assessment of study quality

The authors did not state that they assessed validity.

Data extraction

Percentages were calculated for the number of participants achieving a 50% or greater reduction in cigarette consumption compared with baseline, and odds ratios (ORs) were calculated for abstinence at 6 to 12 months.

The authors did not state how many reviewers performed the data extraction.

Methods of synthesis

Percentages for each outcome were pooled and ORs were pooled for abstinence. Data were reported as a narrative synthesis and in a table. Heterogeneity was assessed using the I2 test.

Results of the review

Five RCTs (n=2,138) were included in the review. The sample sizes ranged from 180 to 269 participants.

At 1 year, NRT was more effective in maintaining reduced consumption of 50% or more of baseline levels than placebo: 16% versus 9%. A modest effect size was also reported for abstinence: 8% for NRT versus 4% for placebo (OR 2.50, 95% confidence interval, CI: 1.69, 3.68). Adverse events were uncommon (reported in 2 studies) and were not significantly different for the two groups.

There was significant heterogeneity between studies reporting a reduction in consumption (I2=67%; p=0.02).

Authors' conclusions

NRT is effective in reducing cigarette consumption through behaviour change and can lead to long-term cessation, which should remain the ultimate goal.

CRD commentary

The review question was clear and was supported by appropriate inclusion criteria for the outcomes, interventions and study design. However, the literature search was limited and, as no apparent search was conducted for unpublished papers, relevant papers might have been missed. It is unclear in which languages publications were sought, thus language bias cannot be ruled out. The validity of the studies was not assessed and the review process for screening and data extraction were not made explicit, which means it is possible that reviewer error or bias may have been introduced. Individual study details and participant characteristics were not reported, which makes it difficult to determine whether they were relevant to the review question and comparable. Given these considerations, the small number of studies and the limited data synthesis, the authors' conclusions may not be reliable.

Implications of the review for practice and research

Practice: The authors stated that the use of NRT to reduce cigarette consumption may be a useful tool for health care professionals who provide advice to smokers in primary care and other community-based health care settings.

Research: The authors did not state any implications for future research.

Funding

One reviewer received travel support from manufacturers of smoking cessation medications.

Medicines and Healthcare Products Regulatory Agency. Report of the Committee on Safety of Medicines Working Group on nicotine replacement therapy: MHRA, Committee on Safety of Medicines, 2005 (cited 2006 Jul 3).

This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.